<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const arr = [1, [10, 20], 2, 3, 4, [5, 6, 7, [8, 9, 0]]];
      // 递归
      // 多维数组的扁平化
      console.log(
        arr
          .toString()
          .split(",")
          .reduce((sum, el) => (sum += +el), 0)
      );
    </script>
  </body>
</html>
